For hemodialysis and other medical procedures, there is the need for chronic, repeated access to the vascular system of a patient. For example, in hemodialysis, access to the patient's blood stream is required generally about three times a week.
Conventionally, this may be accomplished by forming a fistula in an extremity of the patient such as the arm, where an artery and vein of the arm are interconnected. The arterial pressure causes the arm veins to balloon out, and to become good targets for fistula needles, which are commonly straight, sharp needles connected to a length of flexible tubing which, in turn, is connected to an arterial or venous hemodialysis set during use. Alternately, a trocar bearing catheter is used for blood access. The sharp stylet (within a rigid or flexible, dull cannula) provides the cutting means to enter the fistula. Then the sharp, typically hollow-bore trocar is removed leaving the blunt cannula in the vessel.
Two such needle sticks are typically required in a hemodialysis procedure, one for the arterial side, and the other for the venous side, i.e, one to obtain blood from the patient and another to return blood back to the patient.
Significant disadvantages exist with such fistula techniques. Particularly, a direct inter-connection between an artery and a vein places a burden on the patient of the need for additional cardiac output, since some blood is not passing through the capillary system of the body or effectively delivering its oxygen into the tissues.
Accordingly, another type of vascular access is provided, namely implantable vascular access devices such as the vascular device shown in Finch et al. U.S. Pat. No. 5,562,617, Prosl, et al U.S. Pat. No. 4,569,675, and also other known designs of vascular access device. Such a device may comprise an implantable fluid chamber which is connected to a catheter, the system being connected to a vein. Vascular access is provided by a needle which penetrates the skin, and then couples with a port of the fluid chamber, to form an access flow path with the vascular system of the patient through which blood may be removed or replaced. This kind of system has an advantage in that, when it is not connected with a needle, there is no shunting between the arterial and venous system of the patient.
Typically, when a needle does enter such an implanted vascular chamber, it does so at an angle to the skin, from 30.degree. in some devices up to vertical. Accordingly, there is significant advantage in using a needle set in which the needle extends transversely to its set tubing, so that the needle can penetrate the skin in substantially vertical manner, but the set tubing can be basically parallel to the skin. The prior art discloses 90.degree. bent needles for subcutaneous chemotherapy port access devices.
By this invention, an improved set with an angled needle is provided, exhibiting significant advantage of use as a needle for access to a permanently implanted vascular access chamber, to facilitate easy and reliable vascular access.
Another preferred object of this invention is the pre-connection of the needle to a blood tubing set. In the prior art of fistula needles or catheters for access to ports or AV fistulas, the needle set must be a separate device from the blood tubing set. This is required because a "clot worm" must be removed via the female luer that is the proximal termination of such device. Similarly, the "heparin lock" must be delivered through this female luer. Only after these preparation steps are finished can the fistula needle set be joined to the blood tubing set.
Also, it is well known that sharp needles which are brought into contact with blood are potentially dangerous in the event that the needle accidentally sticks a health worker or another person, since this can facilitate the transfer of blood-borne diseases.
Utterberg et al. U.S. Pat. No. 5,112,311 discloses a needle protector comprising a slotted needle sheath which slides longitudinally in the direction of the needle axis along the wings of winged fistula needles, to be advanced into a position that encloses the needle tip as the needle is being withdrawn from a patient. By this invention, sliding or rotating protector systems for angled needles are provided to protect medical personnel and others from accidental needle stick of angled needles, particularly after they have been used in contact with blood.